I doubt if they have any expectations. As many as possible, and that
number will evolve over time with inspection and experience.
On 2015-12-25 11:19, John Dom wrote:
Maybe I missed this Q&A item, but how many times is SpaceX expecting to
reuse its booster? Now or later?
jd
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Rand Simberg
Sent: donderdag 24 december 2015 23:59
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: SpaceX F9 Launch/Update -- Live Link
Max Hunter used to say that he thought static tests for Thor probably
contributed to some flight failures, but as Henry says, those engines had
limited life and number of starts. As far as we know, after twenty
successful flights and one failure, the company has experienced no issues
caused by on-pad static test fire. The one they did last week was obviously
very helpful to them in learning how the subcooled propellants would work in
Florida, and how to tweak their procedures to account for it.
On 2015-12-24 14:53, Henry Vanderbilt wrote:
On 12/22/2015 12:26 PM, William Claybaugh wrote:
On Tuesday, December 22, 2015, David McMillan <skyefire@xxxxxxxxxxxx
<mailto:skyefire@xxxxxxxxxxxx>> wrote:
3. Re-testing. Test-firing one of the SRBs left you with just
as
big a cleanup and refurb task as a full-up STS flight. SpaceX can
(and has, for static test-firings) just keep re-fueling and
re-lighting. About the only thing they can't ground-test is the
hypersonic reentry stresses. In fact, one rumor I heard is that
this stage will be moved to NM and put through multiple "hop"
flight
tests, Grasshopper-style, precisely to see what performance
post-recovery looks like relative to baseline.
Probably irrelevant; no one else static tests before launch and the
risk is generally estimated to outweigh the very limited benefit.
I suggest that no one else static tests before launch because everyone
else till quite recently has been implicitly designing their boosters
for a single use only. While it may not be possible to design every
subsystem to *reliably* last for only one use, the chance that they
may have succeeded for one or more subsystems helps explain the
traditional view that there's too much risk.
Rocket motors in particular can require significant design effort to
ensure that they shut down in a manner that allows for reliable
no-refurb relight. Why bother, if the booster is solely expendable?
If all the subsystems are explicitly designed for relight/reuse, the
risk/benefit calculation changes in a significant way. Static firings
become a useful way of proving many (not all) subsystems are in fact
flight-ready, with (if in fact the design for reuse was good)
little-to-no risk the firing will introduce a problem not previously
present.
Henry